Welcome Fahim. I would also recommend you to join [highlight]
MOCK - MUTT Owners Club Of Karachi
[/highlight]. You can find it in the same forum a few threads up or down.
To begin with, where are you located in Karachi ? Are you running on the original gasoline or have converted ?
As for your problem, it really is a big one. You may have noticed that 80% of the owners here face the same issue. Some have resorted to complete through-out of the diffs with putting in other vehicle diffs (slight modifications) while others have gone ahead with changing the diffs, thwice or thrice. Some are lucky with the take out parts available in the market, some not.
Have you drained the oil completely from the diff and put in new one, straight mineral oil. Not just any gear/transmission oil ?
If you have done each and everything. Then here's a try,........ a real desi totka for problematic diffs (suggested to me by a baloch driver who has done nothing but drive in the vast wilderness)
Take two bottles of 'surma powder' & put that in the diff. In the newer world they put graphite powder in long running gears & turbines. You can also stuff bananas in the diff. The problem is that your diff teeth have given way, probably due to corrosion or exessive use of the clutch. The powder does not mix with the oil, but rather goes and sticks itself to the metal eliminating or decreasing the space between them.
TRY IT OUT, YOU HAVE NOTHING TO LOOSE.
I know people reading this will laugh but i'm saying what people have done & has worked.
If this doesn't work, then I suggest you look to alternative diffs. Mercedes 200 diff is the most favorite of Iranian enthusiasts. Fits with the least bit of alterations.
You can also go with Janj and get the SJ410 diffs in, but I am still to comprehend how a 2400cc transferred to those made for a 1000cc perform. Janj has a low gear installed, maybe that makes a difference.
He has still not explain the complete procedure to us :'(, despite numerous demands. Guess he's busy supplying electric power to the country :S
I'll call you and let meet up sometime.